U.S. Pat. No. 6,402,799 discloses a cyclonic separator in which a gas-liquid mixture is injected via a tangential inlet into a horizontal vortex tube in which the gaseous and liquid fractions are at least partly separated and the liquid fraction forms a film alongside the inner wall of the vortex tube and is discharged via a radial outlet, whereas the gaseous fraction is concentrated near the central axis of the vortex tube and discharged via a central outlet.
International patent applications WO9901194 and WO03029739 disclose cyclonic separators wherein a gas stream is accelerated in a vortex tube to a near sonic or supersonic velocity and thereby expanded and adiabatically cooled such that liquid or solid particles are formed which are discharged via an outlet at the outer circumference of the tube, whereas a dry gas fraction is discharged via a central outlet. These known separators are configured to remove liquefied and/or solidified components from a gas stream and not to remove a gaseous fraction from a carrier liquid.
International patent application WO03/002227 discloses a hydrocyclone for removing air from a high viscosity carrier liquid.
UK patent GB2035150; U.S. Pat. Nos. 2,811,219 and 4,596,586 and International patent application WO03055575 disclose cyclonic separators in which a gas-liquid mixture is injected via a tangential inlet into a vertical vortex tube which has at its upper end a central gas outlet conduit via which the gaseous fraction is discharged and at its lower end a liquid collecting basin which is connected to a liquid discharge conduit.
A disadvantage of the latter group of known cyclonic separators is that they generally are large pieces of equipment and have a limited separation efficiency.
The method according to the preamble of claim 1 and the separator according to the preamble of claim 14 are known from U.S. Pat. No. 6,517,732, which discloses a method of removal of air from blood in a cyclonic device in which first a swirling motion is imposed on the blood-air mixture by helical grooves (24) and the swirling mixture is subsequently accelerated in a nozzle and then separated.
A disadvantage of the known method is that the swirling motion induced by the helical grooves (24) induces dehomogenisation of the fluid mixture by centrifugal forces. Such dehomogenisation before the nozzle reduces the separation performance of the device.
It is an object of the present invention to provide a compact cyclonic separator for degassing a fluid mixture and an efficient method for degassing a fluid mixture.
It is a further object of the present invention to provide a cyclonic separator for degassing a fluid mixture in which a large gas fraction is separated from a carrier liquid.